That was the question — only partly in jest — that circulated back in early 2017 when President Donald Trump nominated Neil Gorsuch to the Supreme Court. The idea — for liberals, anyway — was that Ruth Bader Ginsburg had better stay healthy, or the court's precarious balance would be lost.

Well, after watching "RBG," an engrossing, entertaining and unabashedly adoring new documentary about the now-legendary justice — seemingly a full-fledged pop culture hero at this point — it starts to feel like maybe we're the ones who need the kale. Those who closely follow Ginsburg, now 85, may already know that she works out with a personal trainer, but here we see her actually doing a plank, for what seems like a full minute. Yes, she does pushups too. (Her friends quip that they can't even do half a pushup — either half.)

It's no wonder that the term "superhero" is applied to Ginsburg early in the film, by no less than Gloria Steinem. But in a way, that term doesn't do the justice's story justice. Because superheroes come by their status magically. Ginsburg, we learn here, had to fight every inch of the way, with grit and tenacity and creativity and optimism and lots of all-nighters, over often stunningly difficult obstacles. The best parts of this film show us not how "cool" she is but how hard she worked, and how much she wanted what she got.

Directors Julie Cohen and Betsy West gained impressive access to their subject, with everything from intimate family photos and video to interviews with her children and granddaughter. But we begin with her 1993 confirmation hearing, where she first presented herself to the nation, announcing: "I am a Brooklynite, born and bred, a first-generation American on my father's side, barely second-generation on my mother's."

We then go back to examine her roots. Education was a huge priority in Ginsburg's family; it was where she had her early successes, and a value she obviously passed on to her own children. ("Do your homework," her daughter says when asked what her mother used to tell her. "Don't disappoint us.") We learn that the young Ruth Bader was quiet, polite, determined. "She didn't do small talk," says a friend.

Ruth Bader excelled at Cornell University, where she would meet the love of her life, Marty Ginsburg. The film provides ample proof that this was a truly unusual partnership, based on love and mutual respect as well as Marty's willingness to give his wife's career precedence over his. "He was the first boy I ever knew who cared that I had a brain," Ginsburg says in the film.

Ginsburg went on to Harvard Law School, where she was one of nine women in a class of over 500. Even then, the dean asked the women "why they took a seat that could have gone to a man." She made Law Review her second year, an accomplishment all the more incredible because she was simultaneously doing her own work, taking care of her baby in the afternoons, and doing her husband's law school work for him at night because he was suffering from cancer. She finished her studies at Columbia, and found that despite her accomplishments, no law firm would hire her.

Cohen and West do a deft job of reminding us just what the situation was like for women in the early '60s, when Ginsburg was starting out. And then they show us how slowly, job by job and case by case, Ginsburg went about her life's work fighting gender discrimination — "like knitting a sweater," a friend explains.

It is genuinely thrilling when we hear Ginsburg arguing in the Supreme Court, a young lawyer with a small voice but astonishing confidence. "Are they paying attention?" she admits to wondering at one point, of the silent all-male panel.

Interspersed with the legal stuff is the fun personal stuff: her husband's sense of humor, her intense love for opera, her unlikely friendship with her ideological adversary on the court, the late Antonin Scalia. "What's not to like?" he says at one point. "Except her views on the law!"

But it's her love affair with Marty, who died in 2010, that provides the most inspiring theme of the film. When Ginsburg was appointed to her first judgeship, on the D.C. Circuit, she was often asked if she found it hard to commute from New York — people couldn't imagine that her husband would have moved for his wife's job.

And later, when Bill Clinton was deciding whom to nominate for the Supreme Court, we learn that it was Marty who was his wife's own personal PR agent, contacting everyone he could to get her name out in front. Watching the family hug in the Senate after her hearing, and watching him smile as she's sworn in, it's hard not to feel a lump in your throat.

With the #MeToo movement occupying our culture, it's easy to say that this is the perfect time for a detailed, thorough film on Ginsburg. But frankly, anytime would have been a good time.

And she's doing just fine without the extra kale, thank you very much.

"RBG," a Magnolia Pictures release, is rated PG by the Motion Picture Association of America "for some thematic elements and language." Running time: 97 minutes. Three stars out of four.